Poly(1,4-butylene terephthalate) resins are well known and have been widely employed for the production of thermoplastic molded articles. Poly(1,4-butylene terephthalate) has a good processability, strength and toughness. Other key properties include low water absorption resulting in good dimensional stability, low static and dynamic coefficients of friction, good chemical and abrasion resistance, and good electrical properties.
Polycarbonates are well known and have been widely employed for the production of thermoplastic molded articles.
Polycarbonate is a high-performance plastic with good impact strength. In addition to ductility (impact strength), general-purpose polycarbonate has high transparency, wide temperature limits (high impact resistance below -60.degree. C. and a UL thermal endurance rating of 115.degree. C. with impact), good dimensional stability, high creep resistance and electrical properties which qualify it as sole support for current carrying parts (up to 125.degree. C. without loss of impact strength). Polycarbonate has good stain resistance and a wide range of colorability.
U.S. Pat. No. 3,218,372, which is incorporated by reference, describes compositions of polyalkylene terephthalate and polycarbonate resins. These compositions are described as having a lower melt viscosity as compared with polycarbonate when used alone. Also, this composition is described as having a higher ductility than in the case of the use of polyalkylene terephthalate singly.
However, blends of polycarbonate and polyalkylene terephthalate and particularly poly(1,4-butylene terephthalate) tend to lose their transparency when the composition contains more than about 10% poly(1,4-butylene terephthalate). Transparency is important when compositions of polycarbonate and poly(1,4-butylene terephthalate) are used in packaging applications such as for milk and water bottles. Also, blends of polycarbonate and poly(1,4-butylene terephthalate) lose their optical clarity upon heat aging.